Inborn errors of immunity (IEI) are inherited, monogenetic diseases impair the immune system’s ability to respond. Presentations other than contagious ones are becoming more noticeable. Early indicators that are widely available and affordable are required.

A presenting laboratory finding or an observed secondary manifestation may both represent peripheral-blood cytopenia. Therefore, for a retrospective analysis of the South African Primary Immunodeficiency Registry (SAPIDR), researchers sought to evaluate the hematological indices present at the presentation and their relationship to mortality and the 2019 International Union of Immunological Societies (IUIS) IEI classification.

About 66% (n = 257) of the 396 patients on the SAPIDR had accessible hematological findings. There were 60% men and 85% children under 18. Most people (53%) primarily had an antibody deficit. Infection predominated at presentation (86%) and was followed by cytopenia (62%). IUIS III was linked with neutropenia (odds ratio (OR) 3.65, CI: 1.44-9.25), IUIS II with thrombocytopenia (OR 14.39, CI 2.89-71.57), IUIS I with lymphopenia (OR 12.16, CI 2.75-53.73), and pancytopenia with IUIS I with (OR 12.24, CI 3.82-39.05) and IUIS II (OR 5.99, CI 2.80–12.76). Cytopenia revealed reduced overall survival rates (OR 2.81, CI 1.288–4.16).

Serious, ongoing, atypical, and/or recurring cytopenias should be investigated further for IEI. The complete blood count and leucocyte differential may aid in early diagnosis and work in conjunction with conclusive molecular categorization.